The mayor's spokeswoman declined to specify whether the settlement included a monetary payment, but the Financial Times reported that Johnson was eager to pay the bill ahead of a visit to the United States scheduled for next month.

Last year, Johnson told NPR that officials were "coming after him" for capital gains tax on the sale of his first London home.

Asked whether he would pay the bill, he said: "No is the answer. I think it's absolutely outrageous. Why should I? ... I haven't lived in the United States for, you know, well, since I was five years old."

Johnson, a member of the Conservative Party, has been floated as possible successor to current Prime Minister David Cameron.

This is not the only tax dispute between Johnson and the U.S.

The mayor, known for his unruly blond hair and the occasional gaffe, has criticized the U.S. embassy for not paying the congestion charge -- a levy on vehicles using central London streets during peak hours.

The U.S. embassy, along with other embassies in London, refuses to pay. They say the fee is a form of tax -- and that as diplomats, they are exempt.